Electric Fan

ABSTRACT

An electric fan has an electric motor driving an axial fan. The fan has a cup-shaped hub, with a front wall, and a side wall from which there extends a plurality of outer blades. The motor has an outer rotor including a rotor cap to which the front wall of the hub is attached. From the inner surface of the hub and/or from the outer surface of the rotor cap, there extend protruding formations which, when the fan performs an oscillation of predetermined extent with respect to the rotor, impact the rotor cap and/or the hub, limiting the extent of the oscillation of the fan with respect to the rotor.

CROSS REFERENCE TO RELATED APPLICATIONS

This non-provisional patent application claims priority under 35 U.S.C. §119(a) from Utility Model Application No. TO2014U000060 filed in Italy on Apr. 17, 2014, the entire contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

This invention relates to a fan driven by an electric motor and in particular, to an electric fan for a heat exchanger (such as a radiator) of a vehicle.

BACKGROUND OF THE INVENTION

More specifically, a subject of the invention is an electric fan of the type comprising: an electric motor having an external rotor and an internal stator, and an axial fan including a substantially cup-shaped central hub, with a front wall facing and connected to the rotor, and a side wall which surrounds the rotor and from which a plurality of outer blades extends.

In operation, the motor of such an electric fan generates considerable vibrations, which are transmitted to the fan and bring about the generation of an acoustic noise that is rather annoying for the human ear, particularly at low speeds.

To address this drawback, the Applicant tried connecting the hub of the fan to the rotor of the motor by means of one or more connecting devices that include an elastic vibration damper.

Another known solution instead entails producing at least the hub of the fan from a flexible material, which is likely through its nature to attenuate, at least partly, the vibrations generated by the motor, without resorting to connecting devices provided with vibration damper elements.

The adoption of connecting devices comprising vibration dampers, or of fans with hubs of at least partly flexible material, involves a drawback that, when the motor vehicle on which such an electric fan is installed is subjected to strong angular accelerations, the fan is susceptible to performing oscillations even of notable extent and can collide with surrounding objects and devices, such as the heat exchanger with which it is associated.

SUMMARY OF THE INVENTION

Hence there is a desire for a an electric fan of such a type, produced so as to address the problem, as outlined above.

This is achieved in the present invention by using formations protruding from the inner surface of the hub of the fan, and/or from the outer surface of the rotor of the motor, such that when the fan performs an oscillation of predetermined extent with respect to the rotor, the formations impact the rotor and/or the hub, limiting the extent of the oscillation of the fan with respect to the rotor.

Accordingly, in one aspect thereof, the present invention provides an electric fan comprising: an electric motor including an external rotor and an internal stator; and an axial fan including a substantially cup-shaped central hub, with a front wall, facing and connected to the rotor, and a side wall which surrounds the rotor, and from which there extends a plurality of outer blades, wherein protruding formations extend from the inner surface of the hub of the fan and/or from the outer surface of the rotor, and wherein, when the fan performs an oscillation of predetermined extent with respect to the rotor, the protruding formations impact the rotor and/or the hub, limiting the extent of the oscillation of the fan with respect to the rotor.

Preferably, the rotor of the electric motor has a cap which extends inside the hub of the fan close to the front wall of the hub to which it is connected by means of one or more connecting devices including respective elastic vibration dampers.

Preferably, the or each of the connecting devices comprises an annular damper member of elastic material arranged in a through-opening of the hub, and through which a fastening member passes to fasten the hub to the cap of the rotor. The elastic material may be an elastomeric material.

Preferably, between each damper member and the corresponding fastening member, there is a tubular element of substantially rigid material, for example, a metal material.

Preferably, the fastening member is a screw or bolt having an end head, and the rigid tubular element exhibits at one end a flange-like formation placed between the head of the corresponding screw or bolt and the damper member.

Preferably, the elastic damper member is substantially in the shape of a cylindrical ring, and exhibits an outer peripheral groove into which the edge of the through-opening of the hub is engaged.

Alternatively, the hub of the fan is produced with a flexible material and the rotor of the motor has a cap which extends inside the hub of the fan close to the front wall of the hub, to which it is connected by means of one or more connecting devices.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will now be described, by way of example only, with reference to figures of the accompanying drawings. In the figures, identical structures, elements or parts that appear in more than one figure are generally labeled with a same reference numeral in all the figures in which they appear. Dimensions of components and features shown in the figures are generally chosen for convenience and clarity of presentation and are not necessarily shown to scale. The figures are listed below.

FIG. 1 is a front perspective view of an electric fan according to the preferred embodiment of the present invention;

FIG. 2 is a partial perspective view, in enlarged scale, which shows in particular the hub of the fan of the electric fan of FIG. 1;

FIG. 3 is a partial view in cross-section along the line of FIG. 2; and

FIG. 4 is a partial view in cross-section, similar to that presented in FIG. 3, and shows a variant embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the drawings, an electric fan according to the present invention is indicated as a whole with the reference 1.

The electric fan 1 comprises, in a known way per se, a substantially plate-like support structure or shroud 2, exhibiting a circular main opening 3 at which there is rotatable fitted a fan indicated as a whole with the reference 4. The fan 4 is connected to the rotor of an electric motor which is not visible in FIGS. 1 and 2, but is partially illustrated in FIG. 3, in which it is indicated as a whole with the reference 5.

The electric motor 5 comprises a stator 6, fixed in a known way per se to the support structure or shroud 2, for example by means of a plurality of spokes indicated with the reference 7 in FIG. 1. The motor 5 additionally comprises a rotor, including a cap indicated with the reference 8 in FIG. 3.

The fan 4 comprises a central hub 9, from which there extends a plurality of curved blades 10, the outermost extremities of which meet a peripheral ring 11 (see FIG. 1). The hub 9 is connected to the rotor cap 8 at one or more points or areas of connection.

In the exemplary embodiments of the drawings, the hub 9 is connected to the rotor cap 8 of the motor 5 at three points or areas of connection, indicated with the reference 12 and located at a same distance d from the axis X-X of the fan (FIG. 3). The hub 9 of the fan 4 exhibits a substantially cup-like shape, with a front wall 9 a which is connected with an annular side wall 9 b, which is at least approximately cylindrical.

The rotor cap 8 of the motor 5 extends inside the hub 9, close to the front wall 9 a of the latter to which it is connected at the above said three points or areas of connection 12 by means of devices 13 including respective elastic vibration dampers, which will be better described below.

With reference in particular to FIG. 3, each connecting device 13 comprises an annular damper member 14, of elastic material, in particular of elastomeric material (vulcanized rubber). The or each damper member 14 is arranged in a through-opening 9 c of the front wall 9 a of the hub 9 of the fan. Such a damper member 14 is substantially in the shape of a cylindrical ring, and in its axially intermediate part exhibits an outer peripheral groove 14 a into which the edge of the through-opening 9 c of the hub 9 of the fan 4 is engaged. A corresponding fastening member 15 of the fan passes through the damper member 14 and the rotor cap 8 of the electric motor 5.

The fastening member 15 is for example a screw or a bolt, provided with an end head 15 a.

Between the annular damper member 14 and the screw or bolt 15, there is placed a tubular element 16 of substantially rigid material, such as for example a metal material. The rigid tubular element 16 conveniently exhibits an end flange formation 16 a, placed between the head 15 a of the screw or bolt 15 and the adjacent end of the annular damper member 14. On the opposite side, the tubular element 16 rests on the rotor cap 8.

The threaded stem of the screw or bolt 15 engages in a correspondingly threaded opening of the rotor cap 8.

In the embodiment illustrated in FIGS. 1 to 3, protruding formations 20 and 21 extend from the inner surface 9 d of the hub 9 of the fan 4, in the direction of the rotor cap 8. The distal ends of these formations extend, at rest, to preset distances from the outer surface of the rotor cap 8.

In the exemplary embodiment illustrated, protruding formations 20 extend from the front wall 9 a of the hub 9 towards the corresponding front wall of the rotor cap 8. The protruding formations 21 extend from the inner surface of the side wall 9 b of the hub, in the direction of the side wall of the rotor cap 8.

The arrangement is such that when the fan 4 performs an oscillation of predetermined extent with respect to the rotor, the protruding formations 20 and 21 impact the rotor cap 8 and limit the extent of the oscillation which the fan 4 can perform relative to the rotor.

In a variant embodiment that is not illustrated, protruding formations can be provided on the outer surface of the rotor cap 8, to achieve the same aim. According to a further variant that is not illustrated, protruding formations can be produced either on the inner surface of the hub 9 of the fan 4, and/or on the outer surface of the rotor cap 8.

A further embodiment is illustrated in FIG. 4.

In FIG. 4, parts and elements that are equal to or substantially matching parts and elements already described have been assigned the same reference numbers used previously.

In the variant according to FIG. 4, the hub 9 of the fan 4 is produced with a flexible material, suitable for attenuating, at least partly, the vibrations generated by the electric motor 5.

In this case also, the hub 9 can be connected to the rotor cap 8 of the motor 5 at a plurality of points or areas of connection 12, located at a same distance d from the axis X-X of the fan 4. In the or each point or area of connection 12, the front wall 9 a of the hub 9 is connected to the rotor cap 8 by means of a corresponding fastening member 15, such as a screw or a bolt, with simply a washer 22 interposed.

Also in the embodiment according to FIG. 4, protruding formations 20 and 21, of similar shape and function to those described above with reference to FIG. 3, extend from the inner surface 9 d of the hub 9 of the fan 4.

Also in the case of the variant according to FIG. 4, the protruding formations can be, as an alternative, produced on the outer surface of the rotor cap 8, or both on the inner surface of the hub 9 and on the outer surface of the rotor cap 8.

In the description and claims of the present application, each of the verbs “comprise”, “include”, “contain” and “have”, and variations thereof, are used in an inclusive sense, to specify the presence of the stated item or feature but do not preclude the presence of additional items or features.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.

The embodiments described above are provided by way of example only, and various other modifications will be apparent to persons skilled in the field without departing from the scope of the invention as defined by the appended claims. 

1. An electric fan comprising: an electric motor including an external rotor and an internal stator; and an axial fan including a substantially cup-shaped central hub, with a front wall, facing and connected to the rotor, and a side wall which surrounds the rotor, and from which there extends a plurality of outer blades, wherein protruding formations extend from the inner surface of the hub of the fan and/or from the outer surface of the rotor, and wherein, when the fan performs an oscillation of predetermined extent with respect to the rotor, the protruding formations impact the rotor and/or the hub, limiting the extent of the oscillation of the fan with respect to the rotor.
 2. The electric fan of claim 1, wherein the rotor of the electric motor has a cap which extends inside the hub of the fan close to the front wall of the hub to which it is connected by means of one or more connecting devices including respective elastic vibration dampers.
 3. The electric fan of claim 2, wherein the or each of the connecting devices comprises an annular damper member of elastic material arranged in a through-opening of the hub, and through which a fastening member passes to fasten the hub to the cap of the rotor.
 4. The electric fan of claim 3, wherein the elastic material is an elastomeric material.
 5. The electric fan of claim 3, wherein between each damper member and the corresponding fastening member, there is a tubular element of substantially rigid material.
 6. The electric fan of claim 5, wherein the substantially rigid material is a metal material.
 7. The electric fan of claim 5, wherein the fastening member is a screw or bolt having an end head, and the rigid tubular element exhibits at one end a flange-like formation placed between the head of the corresponding screw or bolt and the damper member.
 8. The electric fan of claim 1, wherein the elastic damper member is substantially in the shape of a cylindrical ring, and exhibits an outer peripheral groove into which the edge of the through-opening of the hub is engaged.
 9. The electric fan of claim 1, wherein the hub of the fan is produced with a flexible material and the rotor of the motor has a cap which extends inside the hub of the fan close to the front wall of the hub, to which it is connected by means of one or more connecting devices. 